Download PST Merge tool to select multiple PST file and merge in one PST file format. You can merge several both ANSI and UNICODE PST file without any data loss and save in safe location of your system.
Now, one can quickly merge multiple PST file into a single PST file by using PST Merge
software. Read more: http://www.osttopstapp.com/pst-merge.html
If you want to merge multiple PST files into a single file, you can use Import feature of Outlook client. It helps you import mailbox content from two or multiple PST files into a single PST file without requiring any 3rd party paid tool. Though it might be a time-consuming task, but still you should try it. To know how to do that, you can read this blog post - Merge PST Files into Single File – Excellent Manual Trick | N. Sem's Blog
If the manual trick takes more than enough time, you can try a professional solution. Download PST Merge software to merge multiple PST files (any number) into a single PST file. It has three options: Merge PST, Joint PST and Merge Contacts. By using demo version, you can save first 5 email items of each mailbox folders of selected PST files into a single PST file. I hope the shared information would be helpful here.
Thanks and best regards.